1. Field of the Invention
The present application is concerned with the transmission of data using forward error correction, that is, where data are encoded using a redundant code such that, upon reception in the presence of errors, the fact that errors have occurred can be recognised at a receiver, and preferably (up to a maximum tolerable error rate) corrected.
The context particularly addressed is where a requirement exists to transmit also auxiliary data also requiring a high level of error protection.
2. Related Art
Error correction coding techniques of many different types have long been used. Some, such as represented by U.S. Pat. No. 5,003,539 (WO,A,87 06368) even use two levels of coding to cause error correction coding to carry additional data. Others use only one level (e.g., U.S. Pat. Nos. 4,271,529 and 3,466,601). Other coding/decoding techniques for conveying extra signalling capacity are also known (e.g., WO,A,93 12598).